With vigorous development of wearable devices (Wearable equipment, WE), the wearable devices are widely applied to daily life of people. However, in consideration of features, such as a small volume, a small battery capacity, and low power consumption of the wearable device, the wearable device cannot directly communicate with a network device in a cellular network. The wearable device needs to communicate with the network device in the cellular network through a relay device, to enable the network device to provide a service for the wearable device. For example, data obtained by a wearable device includes physiological data of a wearer obtained by the wearable device, a relay device may be an intelligent mobile terminal of the wearer of the wearable device, and the wearable device may alternatively be used as a convenient portable communications tool, to provide services, such as short messaging service message receiving, time checking, and location positioning, for the wearer.
In a process in which a wearable device communicates with a network device in a cellular network through a relay device, a non-cellular network protocol transmission technology, for example, a Bluetooth technology, may be used as a communication manner between the wearable device and the relay device. In a Bluetooth technology-based protocol stack, there are various protocol layers, such as a protocol layer of a cellular network, above a Logical Link Control and Adaptation Protocol (L2CAP) layer. Therefore, the L2CAP layer needs to learn of and clarify a specific protocol stack entity to which sent or received data needs to be sent for processing. A protocol data unit (PDU) header of the L2CAP layer includes a protocol/service multiplexer (PSM) domain. A length of the PSM field is 16 bits, some values of the 16 bits have been defined in Bluetooth Special Interest Group (BT SIG), and some other values are dynamically allocated by using the service discovery protocol (SDP). A data packet can be correctly parsed only when both receiving and transmitting parties have consistent knowledge on the PSM field. Therefore, without making a standardized change to the non-cellular network protocol, how to enable receiving and transmitting parties to have consistent knowledge on the PSM field is a problem that urgently needs to be resolved currently.